1. Field of the Invention
The present invention relates to a reverse flow disk in a data storage device and to a head suspension for supporting a read/write head in a reverse flow disk. Airflow induced vibration is reduced over the current state of the art by rotating the disks so that the read/write heads are upstream of the rigid region of the head suspension relative to the air flowing with the disks. Certain flexures and electrical connections enable conventional read/write heads to be used in the present reverse flow disk drive. Additional reductions in airflow induced vibrations can be achieved with the placement of downstream attenuators.
2. Description of the Related Art
Most personal computer systems today employ direct access storage devices (DASD) or rigid disk drives for data storage. A conventional disk drive 20, such as shown in FIG. 1, contains a plurality of magnetically coated recording disks 26 mounted on the spindle for rotation in a direction 24 so that flexure 42 is downstream of load beam 40 relative to airflow 23. The disks 26 could alternatively rotate in a direction opposite to 24 with the airflow 23 also moving in the opposite direction from shown in FIG. 1, provided that head suspension 32 is oriented so that the flexure 42 is downstream of the load beam 40.
The disks 26 contain a plurality of disk features. As used herein, “disk features” refers to discrete magnetic or optical properties of the coated disks. The number of disks 26 and the composition of their magnetic material coating determine, in part, the data storage capacity of the disk drive 20. Positioned adjacent the peripheries of the rotating disks 26 is an E-block 28 having a plurality of actuator arms 30 each supporting one or more head suspensions 32 that extend in cantilever fashion over the disks 26.
FIG. 2 shows the head suspension 32 used to support and properly orient a head slider 34 over the rotating disks 26 of FIG. 1 in more detail. A variety of head suspensions can be used for this purpose, such as disclosed in U.S. Pat. No. 5,920,444 (Heeren et al.). Head suspension 32 has a longitudinal axis 36, and is comprised of a base plate 38, a load beam 40, and a flexure 42. Base plate 38 is mounted to a proximal end 44 of load beam 40, and is used to attach head suspension 32 to the actuator 30 in the disk drive 20. Slider 34 is mounted to flexure 42, and as the disk 26 in the storage device 20 rotates beneath head slider 34, an air bearing is generated between slider 34 and the rotating disk 26 that creates a lift force on head slider 34. This lift force is counteracted by a spring force generated by the load beam 40 of head suspension 32, thereby positioning the slider 34 at an alignment above the disk referred to as the “fly height.” Flexure 42 provides the compliance necessary to allow head slider 34 to gimbal in response to small variations in the air bearing generated by the rotating disk.
Load beam 40 of head suspension 32 has an actuator mounting region 46 at proximal end 44, a load region 48 adjacent to distal end 50, a resilient spring region 52 positioned adjacent actuator mounting region 46, and a rigid region 54 that extends between spring region 52 and load region 48. Resilient spring region 52 generates a predetermined spring force that counteracts the lift force of the air bearing acting on head slider 34. Toward this end, spring region 52 can include an aperture 53 to control the spring force generated by spring region 52. Rigid region 54 transfers the spring force to load region 48 of load beam 40. A load point dimple (not shown) is formed in load region 48, and contacts flexure 42 to transfer the spring force generated by spring region 52 to flexure 42 and head slider 34. A load point dimple can alternatively be formed in flexure 42 to extend toward and contact with load region 48 of load beam 40.
The flexure 42 is formed as a separate component and is mounted to load beam 40 near the distal end 50. Flexure 42 includes a gimbal region 56 and a load beam mounting region 58. Load beam mounting region 58 overlaps and is mounted to a portion of rigid region 54 using conventional means, such as spot welds. Gimbal region 56 of flexure 42 provides the necessary compliance to allow head slider 34 to gimbal in both pitch and roll directions about load point dimple in response to fluctuations in the air bearing generated by the rotating disk. Toward this end, gimbal region 56 includes a cantilever beam 60 having a slider mounting surface to which head slider 34 is attached. Cantilever beam 60 is attached to cross piece 62, which is connected at each end to first and second arms 64a and 64b of flexure 42. Cantilever beam 60 is resiliently movable in both pitch and roll directions with respect to the remainder of flexure 42, and thereby allows head slider 34 to gimbal. Load point dimple (when formed in load region 48) contacts the surface opposite the slider mounting surface of cantilever beam 60 to transfer the spring force generated by spring region 52 of load beam 40 to head slider 34, and further to provide a point about which head slider 34 and cantilever beam 60 can gimbal. In dynamic storage devices optical or magnetic read/write heads 66 are supported on a trailing edge 68 of the slider 34. The trailing edge 68 is defined in relation to the direction 24 that the disk 26 rotates.
A continued trend for greater areal density and faster data transfer rates for rigid disk drives place more demand on suspension windage performance. One way to increase areal density is to increase the number of tracks per inch (TPI), which requires a reduction in track misregistration. The suspension's contribution to off-track due to windage excitation must be maintained within ever-tightening track misregistration requirements. One approach to increase the data transfer rate and reduce latency is to increase the disk RPM. Higher disk RPM can negatively impact suspension windage performance because of increased wind energy. For example, if you spin two identical drives at different RPM, the higher RPM drive is going to create a greater amount of wind energy due to increased disk velocity and therefore higher track misregistration. To satisfy the continuing trends of rigid disk drives, tighter track misregistration will require suspensions that exhibit less off-track due to windage when exposed to increase levels of windage energy due to increasing disk speeds.
Interactions that determine the suspension's windage-driven off-track can be generalized into three separate variables: source energy, energy extraction and the transfer function. Windage off-track occurs due to source energy that originates from fast spinning disks. Turbulent effects of the E-block and other drive features also contribute to source energy. One way to describe the magnitude and influence of source energy is with the Bernoulli Equation. Assume that for any given system, off-track is related to dynamic pressure:
      SourceEnergy    ⁢                  ⁢        ⁢                  ⁢          Pressure      Dynamic        =            1      2        ·    FluidDensity    ·                  (        Velocity        )            2      Fluid density and fluid velocity are the two primary factors, with velocity having a squared effect. For a given suspension, an increase in dynamic pressure will result in an increase in windage off-track (an increase in source energy with all else remaining constant). In terms of windage, the ideal case is to have disks spinning as slowly as possible, thus creating minimal turbulence.
The second variable is the suspension's efficiency to extract energy from the source. Different suspension designs extract different amounts of energy from a given source, depending on part length, surface area, rail height, headlift feature, etc. The third variable is the suspension's transfer function. After a certain amount of wind energy is absorbed into the suspension, the transfer function dictates how it translates to slider off-track. For all suspension modes, the transfer function dictates a given ratio of output per input. The ideal goal is to have output minimized as much as possible by having the ratio as close to zero as possible.
Turning back to FIG. 1, rotation of the disks 26 creates airflow 23 within the disk drive 20. The actuator arms 30 and the E-block 28 channel the airflow 23 toward the head suspension 32. Air flow 23 encounters the E-block 28 and the actuator arms 30 first, with the head suspensions 32 and flexure 42 located downstream of this obstruction. Consequently, the head suspension 32 is located in the E-block's wake. Any turbulent flow generated by the E-block 28 and/or actuator arm 30 can propagate downstream and strike the head suspension 32. The E-block 28 and actuator arms 30 act as funnels to direct more airflow 23 toward the head suspension 32. According to the conservation of mass flow, as the cross-sectional area of the flow region becomes restricted, the fluid density and/or the velocity must increase to account for the smaller cross-sectional area. Increases in these values increase the magnitude of the dynamic pressure acting on the head suspension 32, thus adding to the windage-induced suspension off-track.